Directions: In this question, a sentence has been given with some of its part in bold. To make the sentence grammatically and idiomatically correct you have to replace the bold part with the correct alternative given below. If the sentence is correct as it is, mark 'No improvement required' as your answer.
Important for :
1
The Indian Air Force has played a vital role in the nation’s defense and our glorious history is replete of numerous counts of valour and fortitude in the face of extreme odds.
» Explain it
B
Replete (Adjective):
filled or well-supplied with something. The adjective is generally followed by the proposition 'with'.

Ex. Earth's climate system is replete with potential surprises.

Synonyms:
full, loaded, crowded, abounding, etc.

Moreover, the noun 'account' refers to a report or description of an event or experience and its plural form 'accounts' should be used here in the context. 

Option B would hence make the best choice out of the given options. 
2
Everyone around Sachin in 1988 knew that he would play for India but never thought he would end up with all the cricketing records possible.
» Explain it
E
To end up with someone or something (Idiom):
to finish with the possession of someone or something or in the company of someone or something. 

Ex.  I thought my date was with Ayesha, but I ended up with her twin sister.

The sentence is absolutely correct and hence requires no correction. 

Option E is hence the correct answer.
3
According to WWF, the small island nation of Samoa was the first in switching off its lights in support of the Earth Hour.
» Explain it
B
To express a purpose the infinitive form (to switch off) of a non-finite verb is used instead of the gerund one (switching off). Besides, the correct phrasal verb is 'to switch off' and not 'to switch of'. 

Ex. I come here to study. (Corrrect)
Ex. I come here for studying. (Incorrect)

Option B is hence the correct answer.
4
This pond particularly abounds of large populations of freshwater fish.
» Explain it
C
Options A and B and D can be easily eliminated, as the correct phrasal verb is 'abounds in', and not 'abounds with', 'abounds about' or 'abound through'.

Abound in (Phrasal verb):
To exist in large quantity.

Ex. Other examples of such tall tales abound in the world of coin collecting.

Option C is hence the correct answer.
5
As a component of adenosine triphosphate, phosphorus is critical for the conversion of light energy to chemical energy during photosynthesis, contributes to essential nucleic acids and phospholipids, and hence is important not just for plant growth, but also for flower and seed formation.
» Explain it
E
The original statement is correct and hence, no correction is required.

Hence, option E is correct.